UCLA

This dissertation introduces new approaches for designing a low-cost, low-power, low-noise, and highly linear phased array system for commercial wireless applications. The first approach presents a novel liquid crystal (LC) technology-based structure to reduce the cost, power, and weight of the phase shifter, a critical component in the phased array. LCs, controllable dielectrics with low power consumption, low loss, and cost-effectiveness due to their fabrication using conventional Liquid Crystal Display (LCD) manufacturing technology, enable phase shifting through variations in the main microstrip line’s phase constant, loaded periodically with a variable equivalent capacitance controlled by bias voltage. A systematic approach, utilizing transmission line circuit models and periodic structure theory, is developed for efficient design optimization using advanced design system (ADS) and HFSS software. The fabricated phase shifter achieves animpressive F OM of 105.9 ◦/dB. In the second approach, a modified architecture for a mixer-first phased array receiver is proposed, addressing the demand for high linearity and low noise in commercial wireless applications. Instead of conventional low-noise-amplifiers (LNAs), a new time-variant transmission line (TVTL) mixer serves as the initial stage, showcasing exceptional performance with a broadband conversion gain of up to 4.2 dB, a low noise figure of 3 dB, and an input-referred P1dB of 12 dBm. Additionally, a low-cost, low-power LC phase shifter is integrated into the LO-path, minimizing the impact of lossy phase shifters on receiver noise figures. Finally, the third approach proposes a novel analog beamforming architecture for a low-cost, low-loss, and power-efficient dual-beam phased array system, highly desirable for commercial wireless and satellite applications. This system generates multiple concurrent, independent directive beams with high gain, enabling a terminal to track and connect to multiple base stations, facilitating flexible and broad coverage multipoint communications with improved signal-to-noise ratios. The proposed architecture employs sub-arrays of two antenna elements fed by an orthogonal two-port signal combiner consisting of a 90-degree hybrid block. Each sub-array generates two orthogonal beams, driven by a phase shifter, allowing for the formation of two sharper overall beams and fine, independent scanning within each sub-array beam. Additionally, an optimal antenna array column shift method is proposed to reduce the high side lobes introduced by sub-array usage. Phased array pattern measurements exhibit continuous beam scanning over elevation angles. of 0◦ to 45◦ degrees and azimuth angles of 0◦ to 20◦ degrees for both right and left beams, with a maximum gain of 20.8 dBi and Side-lobe Level (SLL) of −13.7 dB.